The present invention relates to a reinforcing element for a lower region of a front bumper of a motor vehicle for the protection of pedestrians during impact of a lower leg section against the lower region of the front bumper, according to the preamble of claim 1, and a front bumper for a motor vehicle having a first impact region, which is to come into contact with a bumper of a further motor vehicle, and a second impact region arranged below the first impact region, and which is to come into contact with a pedestrian with his lower leg section.
In recent decades the automobile industry has been facing to an increasing extent the protection of pedestrians in accidents. Reducing injury risks during an impact between a motor vehicle and a pedestrian has gained considerable significance over the years.
Hence, it was already discussed, for example decades ago in German Disclosure Number 3 003 568, that in an impact protection device known at that time, the pedestrian protection part should be designed as an upholstered transverse beam, which is arranged lower than the actual bumper and also in front thereof. A pedestrian colliding with the vehicle should thus be caught so deep by this lower transverse beam, that he is not knocked down and then run over, but is tilted onto the relatively soft, deformable vehicle front, as a result of which the danger of injury or at least the severity of the injuries is considerably reduced. These first pedestrian protection parts were in turn not successful, inter alia, because of concerns of the designers and because of manufacturing difficulties and of course the feared impaired aerodynamic properties and a feared impaired force effects of the vehicle front.
At the end of the nineties, international regulation regarding vehicle-side pedestrian protection was discussed together with the European automobile industry. Tests were to be developed, with which a motor vehicle front part may be assessed qualitatively according to the following criteria: a) impact with a lower leg, b) impact with a thigh, c) impact with the hip, and d) impact with the head on a front bonnet of a motor vehicle.
These efforts by the European automobile industry and the legislator resulted finally in the guideline 2003/102/EG for the protection of pedestrians and other non-protected road-users from and in collisions with motor vehicles.
Some of the criteria for assessing the quality of motor vehicle front parts are meant for the requirements for an impact with a lower leg. Hence, at a collision speed of 40 km/hour, the following criteria for the standard ACEA Phase 1 should be fulfilled: a) a dynamic knee-bending angle between thigh and lower leg should be less than 21°, b) shearing in the knee or knee-shearing displacement should be less than 6 mm, and c) acceleration of the lower leg should be less than 200 g (measured at the upper end of the shin-bone). Furthermore, at an impact speed of 40 km/hour, the following criteria for the standard ACEA Phase 2 should be fulfilled: a) a maximum dynamic knee-bending angle between thigh and lower leg of 15°, b) maximum shearing in the knee or knee-shearing displacement of 6 mm, and c) a maximum acceleration of the lower leg of 150 g (measured at the upper end of the shin-bone).
Parallel to the work on guideline 2003/102/EG, embodiments of bumper arrangements which were different from the automobile industry were proposed for a front region of a car encased with a shell. Various examples of this can be found, inter alia, in European granted patent 1 038 732, in European application 1 103 428, in German Disclosure No. 10 304 784, and in European application 1 300 293.
Furthermore, front bumpers for motor vehicles having a first impact region, which is to come into contact with a bumper of a further motor vehicle, have become known from practice, which should also have a second impact region arranged below the first impact region and which is to come into contact with a pedestrian with his lower leg section. The bumper is thus encased with an outer shell, which, inter alia, should ensure an attractive aesthetic external appearance and should guarantee the required aerodynamics. Furthermore, the bumper is supported against a transverse support, which is mounted on the longitudinal supports of the car body by means of crash boxes or the like. The second, lower impact region should thus have a reinforcing element, which is often also designated as a so-called “Lower Bumper Stiffener” (abbreviation: LBS) for “Pedestrian-Protection Lower Leg Impact” or may be designated as a reinforcement of the lower front bumper region for the protection of pedestrians in a leg impact.
An embodiment of such a “Lower Bumper Stiffener” for “Pedestrian-Protection Lower Leg Impact” is discussed, for example in European granted patent 1 038 732 already cited above. The second impact region should thus lie vertically below the first impact region or essentially in the vertical of the latter, that is, the upper and the lower impact region should be arranged exactly above one another, so that the latter form a common vertical front surface towards the front. The lower impact region should thus be formed by the lower part of the bumper, which is mounted as the second lower transverse support below the first transverse support thereon by means of vertically arranged spacers. However, the current strict guidelines for reliable pedestrian protection cannot thus be adequately fulfilled.
Furthermore, in European granted patent 1 038 732, the reinforcing element described there is an integral component of the lower front bumper region, with which it is integrally formed. This integral reinforcing element has a base plate facing towards the ground with the lower side and which terminates the front bumper horizontally. Reinforcing ribs extending in longitudinal direction and arranged parallel next to one another are mounted on this base plate, and extend to the rear starting from a front wall of the lower front bumper and which should ensure stiffening of the base plate with the forward front wall of the lower front bumper. A crossed rib structure is also provided to reinforce the front-side edge region. Finally, the upper and the lower bumper of the front bumper arrangement of European granted patent 1 038 732 are covered externally or towards the front by a common casing designated as a “shield”.
However, such known reinforcing elements have the considerable disadvantage that they are often exposed to considerable mechanical impact stresses from below, which then lead to cracks in the shell structure or in the lower bumper region, due to the necessary low height of the lower impact region above the ground, which has to be selected relatively tightly in order to ensure that a lower leg section, such as for example the ankle, the shin-bone or the calf of a lower leg are struck correctly, for example when driving over today's increasingly high curbs when parking, or for example when driving into a multi-storey car park due to the abrupt change in gradient of the road there of the approach and exit ramps. However, repairs to such reinforcing elements molded in one piece integrally in the front bumper makes the exchange of the entire front bumper necessary, which is associated with considerable costs. The repair costs thus additionally rise, since today's front bumpers are often painted in the color of the car. This brings with it corresponding painting work, which in turn, including corresponding dismantling and assembly work, may easily lead to use stoppage lasting several days, which in the end causes the replacement use of a hired car.
On the whole, particularly from the view of a responsible motorist, who thinks about how he can protect pedestrians and other non-protected road-users by means of passive security installed in the car, an unsatisfactory situation thus exists, which finally produces a rejection stance against motor vehicles and such inadequately designed front bumpers, which in the end in turn makes difficult implementation of corresponding measures for the protection of pedestrians on a broad front.